1. Field of the Invention
The present invention relates to a fuel injection apparatus which boosts fuel stored within a fuel tank by a fuel pump, adjusts a pressure of the boosted fuel to a predetermined pressure by a pressure regulator, and supplies the fuel to an engine via a fuel injection valve, and more particularly to a fuel flow path module used in an inline pump type fuel injection apparatus in which the fuel pump is arranged in an outer side of the fuel tank, and is arranged within a fuel inflow pipe extending toward an outer side from the fuel tank.
2. Description of the Conventional Art
A description will be given of a fuel flow path module in a conventional inline pump type fuel injection apparatus with reference to FIG. 2.
A fuel flow path module M in which a plurality of fuel flow paths are respectively formed independently is formed in the following manner.
Reference numeral 1 denotes a fuel tube portion formed in a tubular shape in a vertical direction. An attaching collar portion 1a formed in a flat shape toward a side portion from an outer periphery of the fuel tube portion 1 is formed in the fuel tube portion 1, and a screw insertion hole 1b is provided through in the attaching collar portion 1a. 
Further, a vapor inflow hole 2, a fuel outflow hole 3 and a regulator fuel inflow hole 4 which are independent from each other are provided from a lower end 1c of the fuel tube portion 1 toward an upper end 1d. 
In other words, the holes 2, 3 and 4 are open to the lower end 1c and the upper end 1d. 
Further, a vapor return joint 5 is pressure inserted to and provided uprightly in an opening portion to the upper end 1d of the vapor inflow hole 2.
The vapor return joint 5 mentioned above is formed by a metal pipe member, and is formed by a straight pipe portion 5a directed toward an upper side, and a U-shaped pipe portion 5b bent in an inverse-U shape from an upper end of the straight pipe portion 5a, and a lower opening portion 5ba of the U-shaped pipe portion 5b is open toward a lower side.
Further, a pressure regulator R is inserted to the opening portion to the upper end 1d of the regulator fuel inflow hole 4 so as to be arranged to be connected.
Reference symbol K denotes a sealed-state pump receiving case arranged at a lower position of the fuel tank T, a fuel inflow hole 6 is open to a lower side of the pump receiving case, and a vapor discharge hole 7 is open to an upper side thereof.
The fuel pump P is provided with a motor Pm and an impeller Pa driven by the motor Pm, and a pressure difference is generated between front and rear sides of a blade groove in an outer periphery of an impeller Pa on the basis of a rotation of the impeller Pa, whereby the fuel is sucked into a pump chamber from a pump suction path Pb, and the boosted fuel is discharged from a pump discharge path Pc. Further, a strainer S is arranged in the pump suction path Pb.
Further, the fuel pump P provided with the strainer S is arranged within the pump receiving case K. At this time, a fuel chamber Ka which can store the fuel is formed between an inner periphery of the pump receiving case K and an outer periphery of the fuel pump P.
Reference symbol D denotes a fuel distribution pipe in which a fuel distribution path 8 is provided. A fuel injection valve J is inserted and supported to the fuel distribution pipe D, and the fuel supplied into the fuel distribution path 8 is supplied toward the fuel injection valve J.
The fuel flow path module M is fixedly arranged in the fuel tank T in the following manner.
A module insertion hole Tb to which the fuel tube portion 1 of the fuel flow path module M can be inserted is provided in a bottom portion Ta of the fuel tank T.
Further, an upper side portion of the fuel tube portion 1 including the vapor return joint 5 of the fuel flow path module M and the pressure regulator R is inserted and arranged within the fuel tank T via the module insertion hole Tb, and an upper surface of the attaching collar portion 1a is arranged so as to be brought into contact with the bottom portion Ta of the fuel tank T via a packing 9. In the state mentioned above, a screw 10 is inserted into the screw insertion hole 1b of the attaching collar portion 1a, and the attaching collar portion 1a is fixed by screw toward the bottom portion Ta of the fuel tank T.
In accordance with the structure mentioned above, the fuel flow path module M is fixedly arranged in the bottom portion Ta of the fuel tank T, the module insertion hole Tb of the fuel tank T is closed by the attaching collar portion 1a, the pressure regulator R including the vapor return joint 5 and the return fuel hole Ra is received and arranged within the fuel tank T, and lower sides of the vapor inflow hole 2, the fuel outflow hole 3 and the regulator fuel inflow hole 4 are open to the lower end 1c of the fuel tube portion 1.
Further, the fuel flow path module M, the pump receiving case K and the fuel distribution pipe D are connected by flow paths in the following manner.
The fuel out flow hole 3 of the fuel flow path module M and the fuel inflow hole 6 of the pump receiving case K are connected by a fuel inflow pipe 11.
The discharge path Pc of the fuel pump P and the fuel distribution path 8 of the fuel distribution pipe D are connected by a fuel outflow pipe 12.
Further, a regulator fuel pipe 13 branched from the fuel outflow pipe 12 is connected to the regulator fuel inflow hole 4 of the fuel flow path module M.
Further, the vapor discharge hole 7 of the pump receiving case K and the vapor inflow hole 2 of the fuel flow path module M are connected by a vapor relief pipe 14.
In accordance with the inline pump type fuel injection apparatus formed in the manner mentioned above, the fuel stored within the fuel tank T is supplied into the fuel chamber Ka of the pump receiving case K via the fuel outflow hole 3, the fuel inflow pipe 11 and the fuel inflow hole 6, the fuel pump P sucks the fuel supplied into the fuel chamber Ka into the fuel pump P via the strainer S and the pump suction path Pb, and the fuel boosted by the fuel pump P is discharged into the fuel outflow pipe 12 via the pump discharge path Pc.
Further, a part of the fuel within the fuel outflow pipe 12 is supplied to the pressure regulator R via the regulator fuel pipe 13 and the regulator fuel inflow hole 4, and is adjusted to a predetermined pressure by the pressure regulator R.
An excess fuel at a time of being adjusted by the pressure regulator R is returned into the fuel tank T via the return fuel hole Ra.
In accordance with the structure mentioned above, the fuel having the pressure adjusted to the predetermined fuel pressure is supplied toward the fuel distribution path 8 of the fuel distribution pipe D from the fuel outflow pipe 12, and the fuel within the fuel distribution path 8 is injected and supplied toward the engine (not shown) via the fuel injection valve J.
On the other hand, if the fuel inflow pipe 11 is warmed up by a heat radiation from the engine or an outside air temperature, a vapor is generated in the fuel flowing within the fuel inflow pipe 11, and the vapor flows into the fuel chamber Ka within the receiving case K from the fuel inflow hole 6.
Further, if the fuel pump P is driven, the motor Pm generates heat, the fuel within the fuel chamber Ka is warmed up on the basis of the heat generation of the motor Pm and the vapor is generated.
Further, if the fuel pump P is driven and the impeller Pa rotates within the pump chamber, the vapor is generated within the pump chamber, and the vapor is discharged into the fuel chamber Ka via a vapor bleeding hole Pd of the fuel pump P.
Further, the vapor generated in the manner as mentioned above is discharged into the fuel tank T via the vapor discharge hole 7, the vapor relief pipe 14, the vapor inflow hole 2 and the vapor return joint 5 through an upper space of the fuel chamber Ka.
Further, in the vapor return joint 5, an upper end of the straight pipe portion 5a is bent in the inverse-U shape toward the lower side by the U-shaped pipe portion 5b. Accordingly, even if the vapor return joint 5 is in a state of being arranged so as to be immersed into the fuel within the fuel tank T, the fuel within the fuel tank T is prevented from flowing toward the inner side of the vapor relief pipe 14.
This is because a peak 5bb of the U-shaped pipe portion 5b is arranged in an upper side of the lower opening portion 5ba. 